Mine prop



Jan. 10, 1967 FRIEDRICH-WILHELM PAURAT 9 MINE PROP Filed Nov. 3, 1965 Friedrich W Pauraf INVENTOR.

Attorney United States Patent 5, 38 Claims. (Cl. 248-354) My present invention relates to the supporting columns or props for mine shafts and tunnels and, more particularly, to yieldable subsurfaces props capable of resisting loads such as those developing in mines and the like upon shifting of soil and rock strata.

It is common practice to provide, in subsurface chambers of the type excavated in mine shafts and tunnels, supporting columns or props designed to hold up the roof strata directly or via the intermediary of beams or the like. Such columns not only have the advantage that they are inexpensive but also are highly satisfactory because they do not materially bend and can be dimensioned to withstand substantially any longitudinal compression. It is, for example, known that the splitting of wooden mine props can be prevented by reinforcing them with a wrapping of a substantially nonyieldable, i.e. nonextensible, winding of wire or the like in order to prevent the splitting of the uprights and to increase the loadcarrying capacity before such splitting commences.

It is, therefore, the principal object of the present invention to provide an improved mine prop which resists buckling and can be made with a predetermined yieldability characteristic and which nevertheless is of relatively simple construction.

I have found that this object can be obtained when, according to the invention, the mine prop comprises an elongated solid body of a compressible material, preferably wood with its grain extending longitudinally, and a hollow-profile elongated member composed of a material substantially more rigid than that of the body (generally steel or other matter) and forced into one end of the elongated solid body so that the material thereof resists further longitudinal displacement of the member into the body; surprisingly, this arrangement provides much better load-carrying capacity and more eifective yield characteristics than do telescoping arrangements wherein the male member is telescopingly received .in a socket-forming female member. In order to take advantage of the compressibility of the material of the solid body, I have found it to be essential to wrap the end thereof receiving the member with a winding of a substantially inextensible flexible elongated element such as strip steel or wire whose preferably helical turns are maintained under tension with the element being anchored to the body. The element thus forms a substantially nonyieldable wrapping which prevents outward displacement of the material of the solid body as the hollow-profile member is driven into the latter thereby insuring that the material displaced by the member is compressed rather than merely pushed away.

According to a more specific feature of this invention, the solid body of compressible material designed to receive the hollow-profile member may be composed of a synethetic resin or some other material mixed with a resinous binder. Thus, sawdust or wood fibers. mixed with phenolic resins, foams of, for example, polystyrene, fiberglass-reinforced epoxy resins and systems in which other resins are substituted for those named, have all been found to be satisfactory.

The wrapping can be effected substantially over the entire length of the solid wooden body or only over limited longitudinal distances so that, for example, the

3,297,292 Patented Jan. 10, 1967 "ice body can be cut between windings or adjacent a winding to the desired length.

According to another feature of this invention, adjustable abutment means are provided on the hollow profile member for limiting the depth of insertion thereof so that in effect accommodation of the prop to the penetration ratio required for the particular application can be obtained.

According to a still more specific feature of this invention, the member is provided with a cross-section-filling body (e.g. diametrically extending rods or coaxial rings) which provide added surface area and constitute compression bodies designed to increase the resistance to penetration by the hollow profile members.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

' FIG. 1 is a vertical elevational view of a mine prop according to the present invention;

FIG. 2 is a detail view of a portion of a mine prop of this type with the wrapping removed;

FIG. 3 is a view similar to FIG. 2 of still another mine prop according to this invention; and

FIGS. 4 and 5 are cross-sectional views taken generally along the lines IVIV and V-V, respectively, of FIG. 1.

In FIG. 1 I show a mine prop which comprises a solid elongated body 10 of wood whose opposite extremities are provided with wrappings or elements 11 and 12 of a steel band 13 and a wire or cable 14, respectively. Each of these elongated elements 'has its free extremity anchored to the body 10 by turns 15 and 16 of the respective windings in a self-clamping manner while pins or screws 17 and 18 hold the other extremities of each of these elements to the wood bod 10 under tension. The self-clamping action is that provided by turns of the winding which overlie the free end thereof and, being under tension, clamp it in place. The windings 11 and 12 are generally helical and prevent outward spreading of the wood body as hollow-profile members 19 and 20 are respectively driven axially into the wooden body 10. In the embodiments illustrated in FIGS. 1, 4 and 5 the members 19 and 20 are tubular and of cylindrical configuration; it will be understood, however, that polygonal cross-sections are also suitable for these elements and may be advantageous depending upon the resistance characteristics desired. The upper element 19 is provided with a fork-like head 21 to receive the usual beam or roof structure and has lugs 22 serving as fastening means for struts or other connecting elements to be bolted to the prop. The bottom member 20 rests upon a dome or dish-shaped footing 23 which may also be rigidly connected to the tubular member 20, e.g. welding.

In FIG. 2, I show a section of a mine prop, which can Otherwise be identical with that illustrated in FIG. 1, in which the insertion portion of the member 19' is formed with axially overlapping and angularly offset slots 24 adapted to receive a Wedge 25 and serving to regulate the length of the prop and the prestressing thereof as previously described. Radial bores and pins may replace the longitudinal slots and wedge shown in FIG. 2. In the arrangement of FIG. 3, the upper end of the solid wooden body 10 is engageable by a collar in the form of a clamping ring 25' which has a tightening bolt 26 for adjusting the permissible depth of penetration by the member 19". As can be seen in FIGS. 4 and 5, over a length of about 10-20 cm. of their insertion portions 19 and 20, each of these tubular members or either of them can be provided with a further compression body such as the ring 27 illustrated in FIG. 4 or the bars 29, 30 of FIG. 5. This ring is held in place by diametral ribs 28 and serves to increase the resistance to penetration by filling part'of the cross-section of the tubularmember. Similarly, the rods 29, 30 (FIG. extending along diameters of the tubular element 20, partially fill the cross-section 'of the latter. and increase the com pressive forces. The upper end of member 20 'is beveled inwardly at 31 to facilitate insertion into the wooden body 10. When in mine tests a prop 'ofthe type shown in FIG. 1 was provided without the mappings, it collapsed after the load increased to 7 /2 metric tons'.'- When wrappings as shown in*the drawing were used, a'compression load of up to 52 tons were satisfactorily withstood and the resistance characteristic were found to .be substantially constant over the practical insertion distance.

The invention described and illustratedi's believed to admit of many modifications within'the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the appended claims.

Iclaim: Y

1. A yieldable mine prop comprising an elongated solid body of a compressible'material; an elongated hollowprofile member composed of a material substantially more rigid than that ofsaid body of a cross-sectional area less than that of said body and forced into the latter at one end thereof whereby the material of said body'resists further displacement of said member into said body, and an elongated flexible element wrapped around at least said end of said body and anchored thereto for resisting outward expansion of 'said'body upon insertion of said member therein.

2. The mine prop defined in claim 1 wherein said body is composed of wood and has its grain running longitudinally in the direction of insertion of said member, said member -being composed of steel, said element being helically wound around said end of said body.

3. The mine prop as defined in claim 2 wherein said 3 element is anchored to said body under tension.

4 e 4. The mine prop as defined in claim 3 wherein said element is anchored at one extremity to said body by turns of the element underlying said extremity and holding it against said body.

5. The mine prop as defined in claim 3 wherein said element is wound only around a part of the axial length of said body.

6. The mine prop as defined in claim 3 further comprising adjustable abutment means on said memberfor limiting the depth of insertion thereof.

7. The mine prop as defined in claimv 6 wherein said abutment means includes an abutment ring clamped around said member.

8. The mine prop as defined in claim 6 wherein said member includes a plurality .of angularly ofiset longitudinally overlapping and-longitudinally extending slots formed in said member, said abutment means including a wedge selectively receivable in said slots.

9. The mine prop as defined in claim ,3 wherein said member is tubular and is provided with a compression body filling part of, the cross-section thereoffor defining the force required to insert said member in said body.

10. The mine prop as defined in claim 3 wherein a similar member is forced into said body from its other end. References Cited by the Examiner UNITED STATES PATENTS CLAUDE A. LE ROY, Primary Examiner. 

1. A YIELDABLE MINE PROP COMPRISING AN ELONGATED SOLID BODY OF A COMPRESSIBLE MATERIAL; AN ELONGATED HOLLOWPROFILE MEMBER COMPOSED OF A MATERIAL SUBSTANTIALLY MORE RIGID THAN THAT OF SAID BODY OF A CROSS-SECTIONAL AREA LESS THAN THAT OF SAID BODY AND FORCED INTO THE LATTER AT ONE END THEREOF WHEREBY THE MATERIAL OF SAID BODY RESISTS FURTHER DISPLACEMENT OF SAID MEMBER INTO SAID BODY, AND AN ELONGATED FLEXIBLE ELEMENT WRAPPED AROUND AT LEAST 